Superconducting qubits can take the form of an oscillator that can transfer energy between some combination of an electric field of a capacitor, a magnetic field of an inductor, and a superconducting phase difference, such as from a Josephson junction. One example of a qubit is a flux qubit (e.g., persistent current qubits). A flux qubit can be configured as a micrometer sized loop of superconducting metal interrupted by a number of Josephson junctions. The junction parameters can be designed during fabrication so that a persistent current can flow continuously when an external magnetic flux is applied. As only an integer number of flux quanta is allowed to penetrate the superconducting ring, a clockwise or a counter-clockwise current is developed in the loop to compensate a non-integer external flux bias. When the applied flux through the loop area is close to a half-integer number of flux quanta, the two lowest energy eigenstates of the loop can correspond to a quantum superposition of the clockwise and counter-clockwise currents.